The present invention is broadly concerned with a pellet implant system that simultaneously administers both an immediate parasiticidal dosage first component and a long term release parasiticidal dosage of a second component placed in subcutaneous pellets in order to control internal and external parasites in domesticated and wild animals. More particularly, it is concerned with an implanter having a pellet magazine containing parasiticidal pellets with an associated injection needle, as well as structure permitting injection of the pellets from the magazine through the needle for implantation under the skin of a animal. The pellets are formulated to deliver two separate doses simultaneously. The first dose is a parasiticidal dose which is immediately available for absorption. The second dose is a parasiticidal dose which is available for sustained absorption through bioerosion and diffusion over an extended period of time.
The importance of parasite control in animals used for meat and other agriculture production, recreation and companionship is well recognized. Meat, milk and fiber producing animals, such as suckling, growing, grazing and feed lot cattle, domesticated swine, sheep, goats, poultry and companion animals such as horses, dogs and cats all serve as hosts for a large number of internal and external parasites. The presence of such parasites is known to reduce overall production in animals producing meat and other agricultural products. In the case of companion and recreational animals, the presence of parasites can lead to discomfort, impaired health and performance, and even death.
Wild animal populations infested with parasites may experience substantial harmful effects as well as reduced reproductive efficiency. Such harmful effects are of particular concern in populations of endangered species, since it may impair attempts to reintroduce the species into an environment or to build the species population up to a level which can be easily sustained by natural growth. Endangered mammalian species which are maintained or managed in limited area preserves such as game preserves, animal parks, national parks or wildlife areas as well as zoo animals which are maintained in confined areas, are particularly susceptible to parasite infestation since they inhabit areas substantially smaller than their natural habitats, with denser populations of both parasites and their animal hosts.
Implant technology, that is to say, subcutaneous implant of pharmaceuticals and medical devices, is now well accepted and widespread in the fields of animal health and production enhancement and human health. Many types of biologically active compounds, including hormones, vitamins, antibiotics, antiinflammatory agents, vaccines and biocides are administered as solid compressed pellets which are injected by an implanter equipped with a hypodermic needle. The needle is used to make a small self-sealing and noncoring implant-receiving puncture beneath the skin at a suitable location on the body of the animal. Small pellets of the bioactive compound are forced through the needle and left under the skin as the needle is removed. The ears are a preferred site for pellet implantation in livestock such as cows, pigs and sheep. Implanted ears are commonly discarded in slaughtering, so that no unabsorbed pellet residue will end up in food products intended for consumption by humans or domestic animals.
The pellets are normally implanted in farm animals while the animal is confined in a chute. An ear is grasped in one hand, and an implanter device having a large hypodermic needle is used to puncture the hide and subcutaneously inject a pellet dose into an implant-receiving puncture. Implantation must be done carefully to ensure that the pellets are properly placed and that no portion of the pellet remains extending from the puncture outside the hide. The procedure must also be carried out quickly since the animals are not entirely cooperative and may shake their heads to free the held ear.
U.S. Pat. No. 5,522,797 (hereinafter xe2x80x9cthe xe2x80x2797 patentxe2x80x9d), and entitled Slide Action Veterinary Implanter, which patent is hereby incorporated by reference, discloses an implanter which employs a slide action mechanism to retract an impeller, store an impeller driving force in a spring in cooperation with a latch mechanism, reset a trigger, and advance a pellet magazine, all by a single trigger actuated reciprocation of the slide mechanism. Operation of the trigger also forces the pellets from the magazine through the needle and under the skin of the animal.
Efficient implanters such as that taught in the ""797 patent permit rapid sequential injection of many animals in a single session and make implant technology particularly well-suited for administration of parasiticides while the animals are confined for ear tagging, branding, veterinary procedures or the like. Even where only a single animal is to be treated, implantation offers a particularly safe method for administering certain biocides, so as to allow a user to avoid biocides that could be toxic if ingested by the animal, for example by licking off residue left on its own hide or fur or on that of another animal following treatment by dipping, spraying or dusting.
A number of effective compounds are available for internal and external parasite control, including the polyketide avermectins, the milbemycins and milbemycin oximes, fenbendazole and lufeneron. The most commonly used avermectins are ivermectin, doramectin, moxidectin, eprinomectrin and abamectin. However, such parasiticidal compounds have not previously been available in implantable pellet formulations which provide for immediate as well as extended release of the parasiticide.
Previous avermectin and milbemycin implants such as disclosed by Hepler in PCT application WO 9625852 and by Wallace in U.S. Pat. No. 4,847,243 do not provide prolonged controlled release of the parasiticide dose. Consequently, additional parasiticidal pellets must be periodically implanted in host animals to treat parasites in the immediate environment of the host animal.
This requirement for periodic readministration is not only cumbersome and inefficient, it increases the likelihood that a dose will be delayed or missed altogether and that parasites endemic to the environment will reinfest the host animal. Moreover, each such procedure subjects the animal to stress and risk of infection at the injection site.
A variety of techniques are currently employed to obtain sustained release of parasiticides. Oral boluses are formulated in double walled cylinders, with layers of racemates of active ingredients, with outer and inner layers having polymer coatings, with wax and fat to retard dissolution, and with a heat responsive carriers.
While such measures provide for sustained release of parasiticides over many hours, they do not obviate the need for periodic redosing. Effective parasite control requires prolonged sustained release for periods of up to several months in order to interrupt the parasite life cycle in the environment of the host animal.
Accordingly, there is a need for a system which delivers subcutaneously pellet implants of varying controlled release parasiticidal dosages to provide immediate as well as sustained release of the parasiticide for a period of up to several months, and which does so without requiring periodic redosing.
The present invention resolves the problems previously outlined and provides a greatly improved parasiticidal pellet system which delivers separate doses of both immediate and long term control of parasite infestation in an animal as part of a single implant procedure wherein the immediate dose is sufficient to kill pests already present in the animal and the long term dose is sufficient to prevent reinfestation.
Broadly speaking, the pellet system includes an implanter apparatus for subcutaneously implanting parasiticidal pellets in an animal through the bore of a hypodermic needle which is operably coupled to a pellet magazine, and a plurality of pellets sized to be implanted through the needle and positioned in the magazine for selective alignment of a pellet with the needle. The pellets include at least one immediate release parasiticidal agent first dose pellet and at least one extended release parasiticidal agent dose second pellet. The combined pellets are packaged in the magazine in an individual dosing chamber for simultaneous delivery of an immediate dose and an extended dose as part of a single injection. Advantageously, the system permits both immediate and sustained release of an effective dose of the parasiticidal agent, in order to control present parasite infestation and release sufficient agent over time to prevent reinfestation for a period of up to about 150 days. The immediate and sustained release agents may be the same or different parasiticidal agents with the principal difference between the agents being that the immediate agent is formulated to completely release into the system of the animal very quickly after implanting to provide a sufficient systemic amount of the immediate agent to kill pests that are currently in the animal and the sustained agent is formulated in a slow release matrix that slowly releases the sustained agent over a comparatively long time, for example about 150 days, in a sufficient amount to systemically prevent reinfestation of the animal.
The principal objects and advantages of the present invention include: providing a multicomponent parasiticidal pellet system; providing a pellet system for immediate as well as sustained delivery of a parasiticide in order to kill both internal and external parasites present on an animal and which may reinfest the animal in the future; providing a pellet system which includes an implanter apparatus for subcutaneously injecting pellets in an animal through the bore of a hypodermic needle which is operably coupled to a pellet magazine and simultaneously introduces separate immediate and extended release parasiticidal pellet doses; providing such a system and method which permits injection of predetermined doses of each of a parasiticide for immediate release and a parasiticide for extended release in a single injection; providing such a system and method which permits subcutaneous injection of both an immediate release parasiticidal dose and an extended release parasiticidal dose; providing such a system and method which permits an operator to selectively inject an extended release parasiticidal dose into the needle; providing such a system and method which permits serial injection of large numbers of animals in a single session; providing such a system and method which may employ a wide range of parasiticidal agents for use in control of infestation; providing such a system and method which is simple and efficient and economical to manufacture, which effectively prevents reinfestation of the animal for a period of up to about 150 days and which is particularly well-adapted for its intended purpose.
Other objects and advantages of this invention will become apparent from the following description taken in conjunction with the accompanying drawings wherein are set forth, by way of illustration and example, certain embodiments of this invention.
The drawings constitute a part of this specification and include exemplary embodiments of the present invention and illustrate various objects and features thereof.